Q. Materials for rain-proof coats and tents owe their water-proof properties to

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Q. RADAR is used for

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Q. Sound of frequency below 20 Hz is called

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Q. On a clean glass plate a drop of water spreads to form a thin layer whereas a drop of mercury remains almost spherical because

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Q. Suitable impurities are added to a semiconductor depending on its use. This is done in order to

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Q. Stars twinkle because

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Q. It takes much longer to cook food in the hills than in the plains, because

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Q. Moment of inertia is

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Q. Of the following natural phenomena, tell which one known in Sanskrit as 'deer's thirst'?

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Q. Inside an aeroplane, flying at a high altitude,

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Q. Sound travels with a different speed in media. In what order does the velocity of sound increase in these media?

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Q. One thousand microns is equal to

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Q. Sound travels at the fastest speed in

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Q. oil raise up the wick in a lamp. The principle involves

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Q. Superconductors are substances which

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Q. Light travels at the fastest speed in

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Q. Railway tracks are banked on curves

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Q. On a cold day when a room temperature is 15oC, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of 15oC, because

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Q. Sound produced at a point is heard by a person after 5 second, while the same sound is heard by another person after 6 seconds. If the speed of sound is 300 m/s, what could be the maximum and minimum distances between the two persons?

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Q. Intensity of sound at a point is ____ its distance from the source.

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